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Register a new userCO2-CH4 conversion and syngas formation at atmospheric pressure using a multi-electrode dielectric barrier discharge
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The conversion of CO2 and CH4 into value-added chemicals is studied in a new geometry of a dielectric barrier discharge (DBD) with multi-electrodes, dedicated to the treatment of high gas flow rates. Gas chromatography is used to define the CO2 and CH4 conversion as well as the yields of the products of decomposition (CO, O2 and H2) and of recombination (C2H4, C2H6 and CH2O). The influence of three parameters is investigated on the conversion: the CO2 and CH4 flow rates, the plasma power and the nature of the carrier gas (argon or helium). The energy efficiency of the CO2 conversion is estimated and compared with those of similar atmospheric plasma sources. Our DBD reactor shows a good compromise between a good energy efficiency and the treatment of a large CO2 flow rate.
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We report on the first observation of white-eye pattern in an air dielectric barrier discharge. The patterned discharges undergo a development as following: random spots - quasihexagonal pattern - hexagonal pattern (type I) - hexagonal pattern (type II) - white-eye pattern - chaos as the voltage is increased. The spatiotemporal characteristics of patterned discharges are investigated by using an optical method. Results show that the two discharge modes, uniform mode and filamentary mode, are actually two different spatial presentations of the same origin: the microdischarge. From the viewpoint of pattern dynamics, the white-eye pattern results from a 3-wave resonance interaction.
CO2/CH4 separation using ionic liquids (ILs) encapsulated metal-organic frameworks (MOFs), especially ZIF-8, has shown promise as a new technique for separating CO2 from CH4. However, the mechanisms behind the high CO2/CH4 selectivity of the method remains indistinct. Here we report the progress of understanding the mechanisms from examining the ZIF-8 aperture configuration variation using DFT and MD simulations. The results indicate that the pristine aperture configuration exhibits the best separation performance, and the addition of ILs prevents the apertures from large swing (i.e. configuration variation). Subsequently, the effect of IL viscosity on the layout variation was investigated. MD simulations also show that the pristine aperture configuration is more stabilized by ILs with large viscosity (0-87Cp). Further increase of IL viscosity above 87Cp did not result in noticeable changes in the aperture stability.
We propose a classification of exoplanet atmospheres based on their H, C, O, N element abundances below about 600 K. Chemical equilibrium models were run for all combinations of H, C, N, O abundances, and three types of solutions were found, which are robust against variations of temperature, pressure and nitrogen abundance. Type A atmospheres contain H2O, CH4, NH3 and either H2 or N2, but only traces of CO2 and O2. Type B atmospheres contain O2, H2O, CO2 and N2, but only traces of CH4, NH3 and H2. Type C atmospheres contain H2O, CO2, CH4 and N2, but only traces of NH3, H2 and O2. Other molecules are only present in ppb or ppm concentrations in chemical equilibrium, depending on temperature. Type C atmospheres are not found in the solar system, where atmospheres are generally cold enough for water to condense, but exoplanets may well host such atmospheres. Our models show that graphite (soot) clouds can occur in type C atmospheres in addition to water clouds, which can occur in all types of atmospheres. Full equilibrium condensation models show that the outgassing from warm rock can naturally provide type C atmospheres. We conclude that type C atmospheres, if they exist, would lead to false positive detections of biosignatures in exoplanets when considering the coexistence of CH4 and CO2, and suggest other, more robust non-equilibrium markers.
Dielectric barrier discharge (DBD) plasma actuators are an attractive option for separation control, lift enhancement, and drag reduction. Some plasma actuators feature optimized electrode shapes, electrical waveforms to maximize the aerodynamic forces at higher angles of attack. Here, we analyze the performance of a direct current augmented DBD (DBD - DCA) actuator with a sawtooth shape exposed electrode. The active electrode was positioned at 18% chord and the electrode at 48% chord of NACA 0012 airfoil. Wind tunnel experiments were conducted at wind speeds of 15 - 25 m/s, corresponding to Reynolds number Re = 201k - 335k. Lift coefficient (C$_L$), drag coefficient (C$_D$), and pitching moment coefficients (C$_M$), were measured with and without plasma actuation for angles of attack $alpha$ = 0$^o$ - 8$^o$ and the DCA electrode potential ($varphi_{DC}$) was varied from 0 kV to -15 kV. With energized DCA electrode, the C$_L$ increases up to 0.03 and the C$_D$ decreases by 50% at 15 m/s flow speeds and 0$^o$ angle of attack, the results are similar throughout the range of $alpha$. The effect of the actuator at higher Re diminishes, suggesting that the maximum control authority could be achieved at lower wind speeds.
Additional material supporting the article Target atmospheric CO2: Where should humanity aim?
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